Unitary magnetizable electric contacts



April 6, 1965 E. FREUDIGER ETAL 3,177,329

UNITARY MAGNETIZABLE ELECTRIC CONTACTS Filed Oct. 12, 1961 United States Patent Filed Oct. 12, 1961, Ser. No. 144,602 8 Claims. (Cl. 200-166) This invention relates to electrical contacts, and with regard to certain more specific features, to weldable unitary magnetizable electric contacts.

Among the several objects of the invention may be noted the provision of electrical contacts incorporating material which is made permanently magnetic in a direction of polarization for purposes when formed into contacts of improving arc control, contact motion control and the like; the provision of an improved solid-phase bonding method of manufacture of such contacts from malleable permanently magnetizable material so as to obtain upon magnetization the maximum or near-maximum magnetic properties of which said material is capable of developing; the provision of contacts of the class described which are weldable without destruction of their magnetic properties to provide for good mechanical and electrical bonds between the contacts made therefrom and their supports; and the provision of permanenly magnetized contacts having adequate bond strength between facing and backing components. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, materials and combinations of materials, the proportions thereof, steps and sequence of steps, features of construction, composition and manipulation, and arrangements of parts which will be exemplified in the constructions, products and methods hereinafter described, and the scope of which will be indicated in the strip, illustrating certain coining and blanking operations;

FIG. 4 is a cross section of a contact made according to the invention;

FIG. 5 is a bottom plan view of FIG. 4;

FIG. 6 is a side elevation of a mounted switch contact made according to the invention; and

FIG. 7 is a plan view of FIG. 3, reduced in scale. Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. Various means have been proposed for incorporating magnetic components in electrical contacts for various purposes such as are control, control of switch movements and the like. Heretofore these have involved comparatively costly and poorly arranged multi-piece structures which have been diflicult to manufacture and assemble.

According to the present invention, the desirable surface material for making and breaking the current, such as fine silver or gold, is solid-phase bonded to a backing material which can be effectively permanently magnetized and which after magnetization is weldable to a contact support Without destroying the magnetic properties imparted thereto. By solid-phase bonding is meant, for example, bonding as set forth in US. Patents 2,691,815

' and 2,753,623. It is to be noted that it is quite difi'icult to clad a conductive material to a permanently magnetizable material which is to be fabricated into a contact having magnetic properties, because of several requirements which must simultaneously be met.

First, a contact having the appropriate magnetic backing material must be made so that it can be magnetized to receive maximum or near-maximum magnetic properties. Second, the combination of the backing and surface material-s must be malleable, so that the combination can be worked by conventional methods, such as rolling, slitting, coining and blanking. Third, the backing material must be weldable without destruction of the magnetic properties, so that good mechanical and electrical joints may be established by automatic methods. Fourth, there must be adequate bond strength between the contact material and its weldable and magnetic backing material.

It has been difficult to meet the above requirements simultaneously, mainly because the ordinary permanent magnetic materials generally are not malleable and have very poor welding characteristics.

Referring to FIG. 1, there is shown at numeral 1 a strip of clean contact material such as, for example, fine silver. This, with a strip of clean magnetizable material 3', is fed through squeezing reduction rolls 5 and 7 to form a reduced composite green-bonded strip 9 having green-bonded components 1 and 3. Before the squeezing operation, the thickness of the fine silver layer 1 may be, for example, .012 inch and the thickness of the layer 3 may be .064 inch. The total thickness of the composite strip 9 after bonding and sintering as it appears in FIG. 2 may be, for example, .064 inch. The width of the bonded strip is arbitrary. In the present example it is sufiicient for subsequent coining and blanking into circular contacts which are .250 inch in diameter. This coining and blanking feature will be developed more in detail below.

A preferred substance for the strip 3 is Cunife alloy, which by weight consists essentially of 60% copper, 20% nickel and 20% iron. Before being subjected to the bonding operation, the Cunife alloy is solution-annealed, and quenched, and cold-rolled. The solution annealing and quenching provide suflicient malleability for the greenbonding squeezing operation.

In order subsequently to obtain desired maximum magnetic properties in the Cunife alloy it should be reduced,

preferably by rolling, such as for example on the order of This is for the purpose of Obtaining proper grain orientation along the strip. This reduction may be accomplished in one or more reducing steps. One or more of these steps may occur (a) during the cold roll ing before being sent to the squeezing rolls 5 and 7, (b)

during the squeezing operation, or (c) afterward. In

the case for which the above dimensions have been given, the larger proportion of the reduction of the Cunife alloy is presumed to have occurred prior to entry into the squeezing rolls 5 and 7, which accords to case (a) above,

leaving a smaller amount to occur between these rolls. If alarge' proportion of this reduction is to occur between .the squeezing'rolls, as in case (b) above, different thicknesses of material entering rolls 5 and 7 are employed, the amounts being calculable by those skilled in the reduction art. On the other hand, a substantial proportion of this reduction may be left to occur after the squeezing rolls Sand 7 have been passed, as in case (c). In such case the final part of the required reduction can be used for the purpose of bringing the composite 'strip 9 to its obtained. The reduction which'occurs by rolling in rolls such as 5 and 7, has for its purpose the generation of a green metallurgical bond, and which contributes to the m3 desired grain-orienting effect. Thus it is apparent that the solid-phase bonding process by rolling has a double function, namely, to effect green bonding and to aid in said desired grain orientation.

The above-mentioned 95% accrued reduction for the Cunife alloy appears to result in the ability later to obtain about the maximum magnetic properties available. With smaller reductions, smaller but often useful percentages of the maximum of the magnetic properties are obtained. However, in the cases of the greater reductions up to the optimum 95% reduction, better alignment of more grains is obtained, such alignment being one ofthe parameters for good magnetic properties. Where cumulative reductions are empolyed, it will be understood that rolling in successive passes should take place in substantially the same direction.

After the composite strip 9 has left the rolls 5 and 7, it is coiled (preferably) and sintered in an appropriate furnace employing a protective atmosphere such as hydrogen or cracked ammonia for preventing oxidation. The sintering step also has two purposes, one of which is to improve the solid-phase bond and another of which is to precipitate a new metallurgical phase in the grainoriented Cunife alloy which makes it magnetizable. In order that such a new phase in the Cunife may be precipitated, the sintering operation should be carried out at lO90 F.-1110 F. for several hours, four hours being suitable. Cooling is effected by permitting the furnace to cool to 600 F. or lower, thus preserving the precipitated phase in the grain-oriented alloy.

A coining operation is illustrated at R at the right in FIGS. 3 and 7, wherein the bonded strip has been diepressed to form a protruding button B having bottom embossing 11 on its magnetizable backing 3. The button B is subsequently punched out as shown by letter L at the left in FIG. 3, to form a separate contact lettered C in FIG. 4. The embossing 11 provides means whereby a good conductive contact is obtained when the contact C is spot-welded, as for example to a switch arm such as shown at W (FIG. 6). The letter S on FIG. 6 indicates a fillet which occurs upon welding. One side of the contact is notched as at N for the purpose of indicating to a user the north polarity (for example) of the magnetic contact. If desired, such polarity may be otherwise indicated. The notch is struck out during the blanking operation (see FIG. 7). p

The magnetization is accomplished by magnetizing individual contacts with polarization in the direction of the grain (FIG. 4) after they have been chopped off or blanked out of the strip. The Cunife alloy, after magnetization, permanently retains itsmagnetic properties. The Cunife component 3 being relatively insensitive to heat retains substantially all of its magnetic properties even when subjected to heating such as caused by spot or like welding conditions occurring during application of the contacts to the switch parts (as illustrated in FIG. 6). The notch N preserves the indication of the direction of polarization in the finished contacts before or after their final mounting.

While Cunife alloy has been described above as being preferable to form the backing layer 3, other Permanently magnetizable alloys may be employed such as Vicalloy I or Vicalloy II. Vicalloy I consists essentially by weight of approximately 9.5% vanadium, 38.5% iron and 52% cobalt. Vicalloy II consists essentially by weight of approximately l3% vanadium, 35% iron and 52% cobalt.

be obtained. Or desired contact movements can be obtained as, for example, final quick-opening and quickclosing actions of thermostatic switches which would otherwise act slowly. It should be noted, however, that the polarization in the plane of the contact, considered as a disc or the like, provides a superior location of poles for applications such as above mentioned. By this means a very close relationship can be established between poles of adjacent contacts for most efficient functioning of magnetic effects. There is also utility in the composite strip as an intermediate product, since it is useful as a purchasable product for formation of contacts subse quently in any desired more or less flat form (discs or the like) which are, or can be, plane polarized along the grain as established along the strip by the rolling operation.

In view of the above, it will be seen that the invention is advantageous for the following reasons, among others: The magnetic component of each contact is metallurgically bonded with its conductive layer, rather than being in the form of a separate piece mechanically or similarly attached as heretofore. The temperature of sintering and Welding is not inimical to the good magnetic properties desired in the contact. Contact manufacture may be conveniently automated because of the simplicity of the rolling, sintering, coining, blanking and magnetizing operations. Production rates may be multiplied by performing the rolling operation on wide strips and slitting them prior to coining and blanking. Economies are effected in that first, the operation of strip reduction in the rolls 5 and 7 serves a double purpose, i.e., to bring about green bonding and at the same time considerable grain orientation. Moreover, the sintering operation also serves a double purpose, namely, to improve the green bond and to precipitate the proper phase in the well oriented alloy, whereby it can be permanently magnetized by applying an appropriate magnetic field.

It is to be understood also that instead of using the v precious metal silverfor the layer .1, other precious metals 1 suitable for electrical contact applications could be used,

such as, for example, gold.

' Utility of the ultimately formed magnetic "contacts rethat .by properly relating the poles of cooperating contacts in a switch, advantageous are blow-out functions may quires no detailed discussion, being known, except to state In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. I

As various changes could be made in the above constructions, products and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: I

1. A unitary magnetizable electrical contact comprising a substantially plane weldable metal backing layer, a substantially conductive metal facing layer, a solid-phase bond therebetween, said backing'layer being grain-oriented in one general direction in the plane of the back-.

ing layer for magnetic polarization along the grain.

2. A contact according to claim 1 wherein the facing layer is selected from the 'group'consisting of silver and gold, and wherein said backing layer is, selected from the group of alloys consisting by weight respectively of substantially copper, 20% nickel and 20% iron; substantially 9.5% vanadium, 38.5% iron and 52% cobalt;

and substantially 13% vanadium, 35% iron and 52% cobalt.

3. A contact according to claim 2, wherein the contact 7 is substantially circular in' outline and marginally notched to indicate the direction of the grain.

4. A unitary magnetizable electrical contact material 7 comprising a substantially plane weldable metal backing layer, a substantially conductive metal facing layer, a sintered SOlld-zPhfiSC bond therebetween, said backing layer having a precipitated magnetizable phase and being grainoriented in one general direction in the plane of the backing layer for magnetic polarization along the grain.

5. A contact according to claim 4, wherein the facing layer isselected from the group consisting of silver and gold, and wherein said backing layer is selected from the groupof alloys consisting by Weight respectively of substantially 60% copper, 20% nickel and 20% iron; substantially 9.5% vanadium, 38.5% iron and 52% cobalt; and substantially 13% vanadium, 35% iron and 52% cobalt.

6. A contact according to claim 5 wherein the contact is substantially circular in outline and marginally notched to indicate the direction of the grain.

7. A contact according to claim 1 wherein the backing layer is an alloy consisting of substantially 60% copper, 20% nickel and 20% iron and the facing layer is silver.

8. -A contact according to claim 4, wherein the backing layer is an alloy consisting of substantially 60% copper, 20% nickel and 20% iron and the facing layer is silver.

References Cited by the Examiner UNITED STATES PATENTS 1,089,907 3/14 Coolidge 200166 1,729,747 10/29 Palm 200166 OTHER REFERENCES German application 1,093,868, Dec. 1, 1960.

BERNARD A. GILHEANY, Primary Examiner. MA-X L. LEVY, Examiner. 

1. A UNITARY MAGNETIZABLE ELECTRICAL CONTACT COMPRISING A SUBSTANTIALLY PLANE WELDABLE METAL BACKING LAYER, A SUBSTANTIALLY CONDUCTIVE METAL FACING LAYER, A SOLID-PHASE BOND THEREBEWTEEN, SAID BACKING LAYER BEING GRAIN-ORIENTED IN ONE GENERAL DIRECTION IN THE PLANE OF THE BACKING LAYER FOR MAGNETIC POLARIZATION ALONG THE GRAIN. 